The use of sealed light sources for various purposes is discussed and illustrated in U.S. Pat. Nos. 3,902,064, 3,902,808, 3,904,907, 3,946,235 3,946,272, 3,984,727, 4,002,922 and 4,024,131 as well as other patents which all issued in the name of the present inventor. Reference is hereby made to these patents for background information relative to the basic operation of such lamps.
In the present invention, the type of lamp generally shown in the above-identified patents is modified so that the central hollow dielectric electrode which has one end enclosed is modified to extend completely through the lamp bulb. Accordingly, the front window which exists in the referenced patents is not used in the present invention. It is effectively replaced by a cylindrical window which will be described below. In the present application, the use of the word "torus" will be basically understood from the dictionary definition which refers to the surface of a solid shape which is normally formed by a revolving plane closed curve about a line in its plane. The structure forming the torus may be shaped by continuous (but not uniform) deformation such that it can be transformed into a torus whose enclosed cross section can be outlined by any plain curve, with or without a tube connecting to the inner wall of the torus.